Adv 2.0 D&D Phase 12 E3a: Sunken Temple tidal event

Adds the §7.1 tidal event hook: warnings on Days 4 and 5, peak event
on Day 6 with forced 2× supply burn (overrides tier-2 HarshMod 1.5×),
silenced if the boss has been defeated.

Wires zone-temporal events into deliverBriefing as two new hook points
— pre-burn (mutates burn multiplier) and post-rollover (appends
flavor-bearing log entries). Future E3b–E3f layer onto the same hooks.

Reuses the prewritten flavor.SunkenTempleTidalWarning / TidalEvent
pools per feedback_reuse_existing_flavor.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/dnd_expedition_temporal.go

@@ -0,0 +1,97 @@
+package plugin
+
+import (
+	"fmt"
+	"strings"
+
+	"gogobee/internal/flavor"
+)
+
+// Phase 12 E3 — Zone-specific Temporal Events.
+// Spec: gogobee_expedition_system.md §7.
+//
+// Temporal events fire at briefing rollover and produce two outputs:
+//   - extraHarsh: forces double supply burn for the burn fired by THIS
+//     briefing (overrides the §4.1 zone HarshMod when the multiplier
+//     should be 2× regardless of tier — e.g. tidal flooding §7.1).
+//   - one or more flavor-bearing log entries (warnings, event narration).
+//
+// applyZoneTemporalPreBurn runs BEFORE applyDailyBurn so the burn
+// reflects the temporal effect for the day being entered. State that
+// persists across days (Heat stacks, Portal instability) is mutated
+// here as well — the per-day increment is the temporal event.
+//
+// Combat-side knobs (tidal +1d6 cold, Underforge +1d4 fire, etc.) are
+// exposed via ZoneTemporalEffects for the combat engine to read; the
+// engine hook lands with the combat-link phase.
+
+// ZoneTemporalEffects bundles the per-zone, per-day combat-side
+// modifications produced by temporal events. Combat code reads this
+// from the active expedition; nothing reads it yet (combat-link phase).
+type ZoneTemporalEffects struct {
+	// TidalActive — Sunken Temple Day 6 only. Combat: +1d6 cold per
+	// turn while wading; kuo-toa +2 AC, +1d4 attack rolls.
+	TidalActive bool
+}
+
+// applyZoneTemporalPreBurn runs at the top of deliverBriefing, before
+// applyDailyBurn. It mutates e (state increments, in-memory only —
+// caller persists the relevant fields) and returns whether this
+// briefing's burn should be force-doubled regardless of HarshMod.
+//
+// nextDay is the day-number we're rolling INTO (i.e. e.CurrentDay+1
+// at call site, since the briefing increments after burn).
+func applyZoneTemporalPreBurn(e *Expedition, nextDay int) (extraHarsh bool) {
+	switch e.ZoneID {
+	case ZoneSunkenTemple:
+		extraHarsh = sunkenTempleTemporalPreBurn(e, nextDay)
+	}
+	return extraHarsh
+}
+
+// applyZoneTemporalPostRollover runs AFTER advance + threat drift.
+// It appends per-zone narration log entries for the day that just
+// became current. Returns lines to append to the briefing body.
+func applyZoneTemporalPostRollover(e *Expedition) []string {
+	switch e.ZoneID {
+	case ZoneSunkenTemple:
+		return sunkenTempleTemporalPostRollover(e)
+	}
+	return nil
+}
+
+// ─────────────────────────────────────────────────────────────────────
+// §7.1 — Sunken Temple, Tidal Event (Day 6)
+// ─────────────────────────────────────────────────────────────────────
+
+// sunkenTempleTemporalPreBurn doubles burn on Day 6 (tidal peak). Skips
+// entirely if the boss has been defeated — the spec's no-op clause.
+func sunkenTempleTemporalPreBurn(e *Expedition, nextDay int) bool {
+	if e.BossDefeated {
+		return false
+	}
+	return nextDay == 6
+}
+
+// sunkenTempleTemporalPostRollover writes warnings on Day 4/5 and the
+// event narration on Day 6. Boss-kill before Day 6 silences all of it.
+func sunkenTempleTemporalPostRollover(e *Expedition) []string {
+	if e.BossDefeated {
+		return nil
+	}
+	day := e.CurrentDay
+	switch day {
+	case 4, 5:
+		line := flavor.Pick(flavor.SunkenTempleTidalWarning)
+		line = strings.ReplaceAll(line, "[N]", fmt.Sprintf("%d", day))
+		summary := fmt.Sprintf("tidal warning — peak in %d day(s)", 6-day)
+		_ = appendExpeditionLog(e.ID, day, "temporal", summary, line)
+		return []string{line}
+	case 6:
+		line := flavor.Pick(flavor.SunkenTempleTidalEvent)
+		_ = appendExpeditionLog(e.ID, day, "temporal",
+			"tidal peak — flooded rooms hostile, supply burn doubled", line)
+		return []string{line}
+	}
+	return nil
+}